Pneumatically actuated percussive tool



Where there is a single valve this efi'ect can only be obtained by making the passage through one valve seat smaller than the other, which has disadvantages.

It is with the invention possible to make the valve movements take place asynchronously.

The invention is illustrated in the annexed drawings, which show two forms of construction in section, in Fig. 1 and in Fig. 2 respectively. I q

Referring first to Fig. l, the cylinder 1 contains the plunger 2, which is driven by compressed air and strikesa tool not shown in the drawings. Compressed air is admitted to the annular distribution spaces 3 surrounding the two valve chambers l and 5, preferably by a channel (not shown) arranged on the cylinder mantle and connecting said distribution spaces. This channel is provided with an air admission pipe (likewise not shown) arranged opposite the exhaust ports disposed in the cylinder wall. In the valve chamber 4 is arranged a ball valve 6 for controlling the working stroke and in the valve chamber 5 a ball valve 7 for controlling the return stroke. Each valve is in its valve chamber exposed on all sides to the compressed air admitted thereto from the distribution space 3 surrounding it. Each of the valve chambers 4 and 5 is provided with a small duct (1 and b communicating with the annular distribution space 3 on the side of the ball valves 6 and 7 opposite to the ports 13 and 17.

The plunger moves in the direction indicated by the arrow for delivering the blow, and is shown at the end of its working stroke. In this position the rear face 8 of the plunger has moved past an exhaust port 9, and owing to the fall of pressure in the cylinder the ball valve 6 is thrust against itsseat 10, cutting off the flow of compressed air to the cylinder. A small duct 11 in thecylinder wall also allows discharge ofair from above the valve arranged in thevalve chamber 5, and this valve is consequently lifted from its seat 12, allowing compressed air to flow through a port 13 and drive the plunger 2 back. In due course the front face 14 of the plunger uncovers an exhaust port 15, and the valve 7 drops back on to its seat 12, cutting off the inflow of compressed air through the port 13, the duct 11 being at this time closedby the plunger. The plunger, moving by virtue of its momentum, uncovers a small duct 16, :which allows air to escape from under the valve 6, so that this valve drops from its seat 10, and compressed air flows through the port 17 for imparting the next working stroke. The valve- 7, admittingair for the return stroke 'of the .plungenvis of smaller diameter than the valve 6," which admits air for the return stroke being commonly less than that required for the working stroke.

Whereas in the construction shown in Fig.

1 the small ducts 11 and 16 are continuously in communication with the compressed air supply pipe, the corresponding ducts 11 and 16 in the modification shown in Fig. 2 are controlled by the ball valves 6 and 7, so that they are only open to the supply pipe While compressed air is being supplied to those parts of the cylinder int-o which they lead. This saves loss of compressed air, and increases the eiiectivesupply to the cylinder. The mode of operation is substantially the same as described with reference to Fig. 1. vThe plunger is shown in a position in the course of the working stroke, with the valve 7 resting on its seat 12, and thevalve 6 dropped from its seat 10 on to a seat 10. lVhen the plunger uncovers the exhaust port 9 both the valves 6 and 7 are lifted, and the valve 7, held against a seat 12, prevents further fiow of air through the duct 11 to the top .of the cylinder, whereas air flows through the port 13 to the bottom of the cylinder, which also receives a small amount of air through the duct 16, previously cut off from the air supply by the ball 6 resting on the seat 10.

The valve seats 12, 12, 10 and 10 may be so proportioned that the valves 6 and 7 open and close at diiferent times. The valve 7 is shown as having only a very small movement, the amount of air required for the re- .turn stroke being small.

Broken lines in Fig. 2 indicate a further .modification wherein the small duct of the valve chamber 5, designated 11", opens into .the cylinder below the upper exhaust port 9. This modification is particularly suited for pneumatic hammers with a long stroke. The effect thereof is that the valve 7 is not opened till the plunger has reached the end .of the power stroke. When the plunger clears the port 9 there is at first only a small admission of compressed air in front of it, through the duct 16, the port 13 remaining closed, so that admission from this port does not impede the final stage of the plunger movement. The positions in which the small ducts open into the cylinder are of course always arranged in accordance with the particular work for which the apparatus is designed. 1

It will be clear that valvesother than ball valves may be used, and that the valves may be placed in any convenient position, e. g., both on the same side of the cylinder. The drawings are in this respect purely diagrammatic. In some cases it may be desirable .to duplicate the valves, that is to say to have two groups of valves instead of two single valves, the valves in each group being in for the workingstroke, the powerrequired parallel.

in the first named valve chamber for control ling the working stroke, and a floating valve arranged in the second valve chamber for controlling the return stroke and adapted to operate independently from the valve controlling the working stroke, of which valves each is adapted to change its seats when the main air inlet port of the one valve chamber and the relief duct of the other valve chamber are put in communication with the same exhaust port by the withdrawal of the plunger from the cylinder chamber into which they open and each valve is adapted to close the relief duct of its valve chamber except when the cylinder chamber to which said relief duct leads is receiving compressed air from the main air inlet port of the other valve chamber.

2. A pneumatically actuated percussivetool, comprising a cylinder, a plunger recip rocating in said cylinder, a valve chamber communicating with the rear cylinder chamber by a main air inlet port and with the front cylinder chamber by a relief duct, a second valve chamber communicating with the front cylinder chamber by a main air inlet port and with the rear cylinder chamber by a relief duct, a ball valve arranged in the first named valve chamber for controlling the Working stroke, and a ball valve arranged in the second valve chamber and executing a smaller lineal movement than the ball-valve controlling the working stroke and adapted to operate independently from the last named ball valve, of which valves each is adapted to close the relief duct of its valve chamber except when the cylinder chamber to which said relief duct leads is receiving compressed air from the main air inlet port 'of the other valve chamber.

3. A pneumatically actuated percussive tool, comprising a cylinder, a plunger reciprocating in said cylinder, a valve chamber communicating with the rear cylinder chamher by a main air inlet port and with the front cylinder chamber by a relief duct, a second valve chamber communicating with the front cylinder chamber by a main air inlet port and with the rear cylinder chamber by a relief duct, a floating valve arranged in the first named valve chamber for controlling the working stroke, and a floating valve arranged in the second valve chamber for controlling the return stroke, each of said valves being adapted to change its seats when the main air inlet port of the one valve chamber and the relief duct of the other valve chamber are placed in communication with the same exhaust port by the withdrawal of the plunger from the cylinder chamber into whch they open, and each valve chamber having a duct therein communicatin with the air inlet and constantly on a si e opposite to the inlet ports.

In testimony whereof I afiix my signature.

JOSEF KoHLEN. 

